1. Field of the Invention
The present invention relates to a wire stripper and, more particularly, to a laser wire stripper that does not involve the rotation of either the wire or the laser to accomplish a complete circumferential cut.
2. Description of the Prior Art
Laser wire stripping devices have a number of advantages over conventional wire stripping equipment. If used properly, the laser cuts only the insulation around the wire and does not have any effect on the wire itself. As a result, the possibility of nicking or cutting the wire is virtually eliminated. Laser strippers cut insulation, such as kapton, fabric covers and Teflon, that is difficult to strip conventionally. Lasers can strip very small wires because location of the wire at the focal point of the laser beam is not critical so long as it is close enough for the laser energy to vaporize the plastic insulation. Many laser strippers can also be used for center stripping and for stripping ribbon cables. Laser strippers are fast and reliable, and do not depend on the condition of blades that must be kept sharp. One way that lasers can be used to cut the insulation and not the wire is, for example, use of CO.sub.2 lasers operating in the infrared region. This comes about because the insulation has low thermal conductivity, a low vaporization temperature and a high absorption of heat compared to the wire itself which has a high thermal conductivity, high melting temperature and a low absorption of radiant energy. Some newer lasers emit light in the ultraviolet region, and at these wave lengths the plastic insulation may be cut by disassociating the molecules rather than by vaporizing with heat. This is particularly desirable for very fine wires, e.g. 40 gauge and smaller, insulated with kapton.
The prior art includes three general kinds of laser wire strippers as follows: (1) Systems utilizing a laser and rotating the wire under a stationary beam. These systems have the drawback that the wire must be rotated and accurately positioned, which is often difficult to accomplish. (2) Systems in which the laser beam itself is rotated around the wire. Such systems have advantages where stationary shielded wires are to be stripped or where good control of the energy is required to prevent burning through the inner insulation. Such systems are very difficult to automate and require rather accurate wire location. (3) Systems utilizing a stationary laser, a stationary wire and a beam splitter to divide the laser beam into two portions each of which contains half the power. The two separate beams are generally directed so as to approach the wire from opposite directions and the beams are usually focused to a point in the center of the wire. Instead of rotating the wire, the wire is moved transversely across the laser beams and, accordingly, the insulation is cut on both sides at the same time. This has a number of advantages over the rotating wire or rotating laser system because it is more versatile, may be used for ribbon cable as well as round wire, allows for easy control of the strip length and is insensitive to the position of the wire. Even if the wire is out of position relative to the focus, it still gives a good cut as the top and bottom cuts still meet on the other side. Furthermore, the insulation can be cut lengthwise and, accordingly, center stripping is possible. The main difficulty with this system is the expense associated with having a beam splitter and three additional mirrors and two lenses.